Reservoir container material for hydrogen filled devices



June 25, 1963 J. E. CREEDON ETAL 3,095,518

RESERVOIR coummma MATERIAL FOR HYDROGEN FILLED osvxcss Filed Jan. 4, 1961 FIG. 2

Q pnessum-z GAUGE Q Q THYRATRON RESERVOIR CONTAINER AND HEATER ASSEMBLY GLASS TUBING INVENTORS,

JOHN E CREEDON s01. same-men a NORMAN L- YEAMANS.

A T TORNE X United States Patent 3,095,518 RESERVOIR CONTAINER MATERIAL FOR HYDROGEN FILLED DEVICES John E. Creedon and So] Schneider, Little Silver, and Norman L. Yeamans, Asbury Park, N .L, assignors to the United States of America as represented by the Secretary of the Army Filed Jan. 4, 1961, Ser. No. 80,710 8 Claims. (Cl. 313-180) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention relates to hydrogen filled devices such as thyratrons, and other hydrogen filled devices such as rectifiers, clipper diodes and the like, and more particularly, to novel reservoir container materials for such devices.

A common cause of failure in the operation of devices of this kind is the reduction of the pressure of the gaswas filling due to the deleterious effects of clean-up of the hydrogen on the envelope and electrodes of the device, which below a certain pressure results in an increase in the potential required to initiate the discharge of the tube and/or causes excessive anode dissipation. This increased potential requirement may itself result in failure to operate, or the increased temperature of the anode which results may cause the liberation of gases from the anode which poison the cathode or results in distortion of the anode. Cleanup is not foreign to tubes using other gases, but in the case of hydrogen, a reservoir can be used to compensate for the gas lost in the cleanup phenomena. The reservoir or exothermic occluder consists of a heated hydrogen compound. The equilibrium hydrogen vapor pressure obtained depends on the temperature of the system and the amount of hydrogen in the occluder.

In addition to supplying hydrogen to compensate for cleanup losses, the reservoir must be capable of maintaining the pressure within a narrow range. For a thyratron, the range extends from approximately 300 to 800 microns. High voltage hold-0E requirements restrict the upper pressure limit, and the lower limit is defined by either trigger requirements, or the appearance of excessive anode dissipation. A further requirement placed on the resirvoir is that it should be capable of operating at a high ambient temperature, in the case of a thyratron, about 700 C. This requirement is brought about by the necessity for the reservoir to operate in an atmosphere whose ambient temperature is mainly determined by the hot cathode located in its vicinity.

The general properties of an ideal reservoir for a practical device may be described as follows:

(1) The reservoir must be capable of storing large quantities of hydrogen to compensate for losses that are due to cleanup. Although this may be expressed in several ways, it is generally referred to as the loading expressed in liter-millimeters per gram.

(2) The reservoir must be capable of releasing the gas in a controllable and predictable manner. For an exothermic occluder, hydrogen is evolved by raising the temperature of the material, usually by means of an externally controlled heater.

(3) The reservoir should be capable of operating at high ambient temperatures, approximately 700 degrees centigrade, and, for a given temperature, the resulting equilibrium pressure should be independent of the loading.

(4) The equilibrium pressure obtainable should include the pressure region from 300 microns to 800 microns.

3,095,518 Patented June 25, 1963 (5) The change in pressure resulting from a change in temperature should be small.

(6) Handling, processing, and cost of the material should be practical.

It has recently been indicated that rare earth metals have pressure-temperature loading characteristics making them suitable for use as the reservoir in hydrogen thyratrons. The rare earths include elements 57 through 71 in the periodic table; namely, lanthanium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Their use as the reservoir in hydrogen discharge devices, as, for example, thyratrons, is discussed in US. Patent 2,919,368 to S. Goldberg and E. J. Goon.

Although the rare earths are suited for use as the reservoir for hydrogen filled gaseous discharge devices, their ready reaction with most materials normally used in tube technology introduces a container problem. That is, the use of containers commonly used for reservoir materials, as, for example, nickel or tungsten in the case of the rare earths, causes a strong reaction and may even destroy the container. The rare earth becomes alloyed and then loses its ability to absorb and desorb hydrogen both necessary for proper tube operation. This difficulty is especially marked where it is desired to operate the tube or thyratron over a period in excess of 1000 hours.

An object of this invention is to provide a long life container for the rare earth reservoir of a thyratron or other hydrogen filled device. A further object is to provide such a container for the rare earth reservoir so that a thyratron containing the reservoir will be able to operate at a pressure of 300 to 800 microns and at a temperature about 700 C. for a period in excess of 1000 hours.

We now find that the above objectives can be attained and the container difiiculties encountered when using the rare earths overcome by enclosing the rare earth reservoir in a container comprising a rare earth oxide coating. By enclosing the rare earth in a rare-earth oxide container, the rare earth reservoir can operate the thyratron at a pressure of 300 to 800 microns and at a temperature about 700 C. for a period in excess of 1000 hours.

The particular rare earth oxide used as the container material is not critical. Very desirable results have been obtained using dysprosium oxide. Similarly, desirable results have been obtained using mixtures of rare earth oxides.

The container can be made of rare earth oxide coating alone, as, for example, a crucible formed of rare earth oxide without any substrate; but preferable, the rare earth oxide is coated onto a suitable substrate and the coated substrate serves as the container. Of course, when a substrate is used, it must be easily formed and must retain its physical properties in a hydrogen atmosphere at the desired temperature of operation of the tube. Nickel has been found to be a very suitable substrate.

The invention can be best understood by referring to the accompanying drawing.

In the drawing,

FIG. 1 is a cross-sectional view of a gas reservoir memher in a reservoir container and heater assembly that has been found useful for thyratron operation.

FIG. 2 is a schematic representation of simple laboratory apparatus showing how the reservoir member, reservoir container and heater assembly in FIG. 1 may be used with the thyratron in a closed system while observing the temperature and pressure of operation of the latter.

In FIG. 1, a rare earth, as, for example neodymium 10, is positioned within a container 11, which is fabricated from a sheet of 0.005 inch thick nickel which has been degreased and flame sprayed to obtain a coating of approximately 0.001 inch of dysprosium oxide. It is not found necessary to sinter the sprayed metal, which is cut to size, rolled to shape, and either spotwelded or held together with nickel bands. Nickel spacers 12, coated with rare earth oxide and with provision for gas leakage are utilized to position the neodymium in a constant temperature region and prevent spillage of the neodymium. Heater coils 13 with leads 14 and located on the outside of the container supply the required heat for activation of the reservoir member. To control the heat liberated, the heater coil is surrounded by heat shields 15. The temperature of the reservoir member is indicated by the thermocouples 16 leading into the reservoir member, and the temperature of the heater coils observed through a peep hole 17 located in the heat shield. End caps 18 are positioned at each thermocouple end. Holes in the end caps through which the thermocouple leads pass also permit gas to enter and leave the reservoir member.

The reservoir member, reservoir container, and heater assembly as shown in FIG. 1 is then ready for incorporation into the thyratron tube. It is possible, of course, to eliminate the peep hole and thermocouples shown in FIG. 1 from the reservoir member, container, and heater assembly when placing the latter within the tube proper of the thyratron. This would occur when it is not necessary to observe the temperature of thyratron operation. Such may be done in practice in a manner similar to that shown in US. Patent 2,919,368 to S. Goldberg or US. Patent 2,497,911 to G. J. Reilly. The particular position of the reservoir member, reservoir container and heater assembly in the thyratron can be varied depending on the degree of thermal isolation desired from the heat emitted from the cathode. Thus, if one wishes to take advantage of the heat emitted by the cathode for heating the reservoir member, he will place the reservoir member, reservoir container and heater assembly closer to the cathode, and vice versa.

To observe the pressure and temperature during operation of the thyratron, simple laboratory apparatus may be used of which FIG. 2 is a schematic representation. In FIG. 2, the reservoir member, reservoir container, and heater assembly 19, is connected to the thyratron 20 by glass tubing 21, in which a pressure gage 22 is inserted. The whole system is closed and kept under vacuum. Prior to operation of the thyratron, an external source of hydrogen is passed into the vacuum system and absorbed by the reservoir member. The external source of hydrogen is then shut off, the vacuum system sealed, and the thyratron operated by the hydrogen evolved from the reservoir member.

When the rare earth is used as the reservoir member within the rare earth oxide coated nickel container, as shown in the apparatus of FIG. 2, an ideal reservoir is obtained. That is, the reservoir operates the thyratron at a pressure of 300 to 800 microns and at a temperature of about 700 C. for a period in excess of 1000 hours. Especially desirable results have been obtained using neodyrnium or dysprosium as the reservoir member in a nickel container coated with dysprosium oxide or mixture of rare earth oxides. Such mixtures of rare earth oxides are marketed by the Lindsay Chemical Division of the Americal Potash and Chemical Company under 4 the trade name Lindsay Codes 330, 331 and 4 20. Lindsay Codes 330 and 331 are mixtures of rare earth oxides in which the major constituent is certain oxide. In Lindsay Code 420, the major constituent is lanthanum oxide.

What is claimed is:

1. In a gaseous discharge device including a closed vessel containing a plurality of electrodes and a hydrogen gaseous medium of a pressure of 300 to 800 microns, a gas generating source comprising a gas reservoir member, said member comprising a rare earth metal containing absorbed hydrogen gas, a rare earth oxide container for the gas reservoir member, and means for operating the reservoir member at about 700 C. to 800 C.

2. In a discharge device including a closed vessel containing a plurality of electrodes and a hydrogen gaseous medium of a pressure of 300 to 800 microns, a gas generating source comprising a gas reservoir member, said member containing absorbed hydrogen gas, a rare earth oxide coated container for the gas reservoir member, and means for operating the gas reservoir member at about 700 C. to 800 C.

3. A gas generating source according to claim 2 wherein the rare earth oxide coated container for the reservoir member consists of dysprosium oxide coated on a nickel substrate and where the gas reservoir member is neodymium metal containing absorbed hydrogen gas.

4. A gas generating source according to claim 2 wherein the rare earth oxide coated container for the reservoir member consists of dysprosium oxide coated on a nickel substrate and where the gas reservoir member is dysprosium metal containing absorbed hydrogen gas.

5. A gas generating source according to claim 2 wherein the rare earth oxide coated container for the reservoir member consists of a mixture of rare earth oxides coated on a nickel substrate and where the gas reservoir member is neodymium metal containing absorbed hydrogen gas.

6. A gas generating source according to claim 2 wherein the rare earth oxide coated container for the reservoir member consists of a mixture of rare earth oxides coated on a nickel substrate and where the gas reservoir member is dysprosium metal containing absorbed hpdrogen gas.

7. A discharge device comprising a closed vessel containing a plurality of electrodes and a hydrogen gaseous medium of a pressure of 300 to 800 microns, a gas generating source for the discharge device comprising a gas reservoir member comprising a rare earth metal containing absorbed hydrogen gas, a rare earth oxide container for the gas reservoir member, and means for operating the gas reservoir member at about 700 C. to 800 C.

8. A discharge device comprising a closed vessel containing a plurality of electrodes and a hydrogen gaseous medium of a pressure of 300 to 800 microns, a gas generating source for the discharge device comprising a gas reservoir member comprising a rare earth metal containing absorbed hydrogen gas, a rare earth oxide coated container for the gas reservoir member, and means for operating the gas reservoir member at about 700 C. to 800 C.

Reilly et al. Nov. 7, 1950 Palmer Aug. 27, 1957 

1. IN A GASEOUS DISCHARGE DEVICE INCLUDING A CLOSED VESSEL CONTAINING A PLURALITY OF ELECTRODES AND A HYDROGEN GASEOUS MEDIUM OF A PRESSURE OF 300 TO 800 MICRONS, A GAS GENERATION SOURCE COMPRISING A GAS RESERVOIR MEMBER, SAID MEMBER COMPRISING A RARE EARTH METAL CONTAINING ABSORBED HYDROGEN GAS, A RARE EARTH OXIDE CONTAINER FOR THE GAS RESERVOIR MEMBER, AND MEANS FOR OPERATING THE RESERVOIR MEMBER AT ABOUT 700*C. TO 800*C. 